class AtlCtrlPlots: public AtlAnalysisTool

 Helper class for control plots common for all ATLAS analyses.
 Used by AtlSelector.

 See the class descriptions of AtlSelector and AtlExampleAnalysis
 how to use this class in your analysis job.

 When being used this class appends an additional directory
 structure to the output file in which the control histograms are
 stored. This new structure is basically divided into two
 paren-folders. One for all histograms filled without any selection
 cuts, and the other one containing a doubled of all histograms
 which are filled after the AtlSelector::ProcessCut() method call,
 ie. after event selection.

     CtrlPlots
       |
       |
       +--- NoEvtSel
       |       |
       |       +--- Jet histograms
       |       |
       |       +--- Electron histograms
       |       |
       |       +--- ...
       |
       |
       +--- EvtSel
               |
               +--- Jet histograms
               |
               +--- Electron histograms
               |
               +--- ...

 In order to append control histograms perform the following steps.

 (1) Switch the necessary branches on by adding the respective lines
 to the SetBranchStatus() member function.

 (2) Extend the BookHistograms() and BookXXXHistogram() member
 functions. Do not forget to add the histogram to the
 fHistogramsNoEvtSel list. You must NOT give the same name to
 more than one histogram.

 (3) Extend the FillHistograms() and FillXXXHistograms() member
 functions accordingly. The histograms are accessed by their names.

 Note: All histogram have to be booked and filled only once. The
 second set (which will be filled after the event selection) is
 booked and filled automatically.


 Author: Oliver Maria Kind <mailto: kind@mail.desy.de>
 Update: $Id: AtlCtrlPlots.cxx,v 1.77 2015/04/22 21:16:52 stamm Exp $
 Copyright: 2009 (C) Oliver Maria Kind